Removal of sodium sulfate from solution



UNITED STATES PATENT OFFICE.

FRANCIS ARTHUR FREETH, 0F SANDIWAY, AND HERBERT EDWIN GOCKSEDGE, OFLONDON, ENGLAND.

REMOVAL OF SODIUM SULFATE FROM SOLUTION.

No Drawing.

7 '0 all whom it may concern:

Be it known t at we, FuANcis ARTHUR FREETH and HERBERT EDWIN CooKsEnoE,both subjects of the King of Great Britaimand residing, respectively, atSandiway, Cheshire, and London, both in the Kingdom of England, haveinvented certain new and useful. Improvements in or Relatin to theRemoval of Sodium Sulfate from olution, of which the following is aspecification.

We have discovered a process whereby it is possible to extract sodiumsulfate, without evaporation or cooling, from a saturated or nearlysaturated solution of that salt, which solution may or may not containother salts or substances.

Our process is as follows We take any solution which is saturated, ornearly saturated with sodium sulfate at any given temperature and whichmay or ma not contain other salts or substances an digest it at, orslightly above such temperature with a quantlty of calcium sulfate,(preferably, but not necessarily anhydrous) suflicient to form-thed0uble salt of the formula CaSO Na SO commonly known as glauberite,and to leave a small excess of solid calcium sulfate. The solution afterremoval of the precipitate of calcium sodium sulfate admixed with asmall quantity of calcium sulfate can then be used for any purpose forwhich it is desirableto have a solution containing less sodium sulfatethan corresponds to saturation at a particular temperature. v

Instead of forming the double salt CaSO,Na SO, by the addition ofcalciumsulfate as such to the solution from which the sodium sulfate isto be removed, we may form the double salt by addition of any othercalcium salt (such forinstance as calcium chlorid or calcium nitrate)which reacts with sodium sulfate to form calcium sulfate,. rovidcdalways that this alternative is confined to cases where the othercompound formed by the reaction (for example sodium chlorid when calciumchlorid is used, or sodium nitrate when calcium nitrate is used) is notdeleterious to the purpose for Specification of Letters Patent.

Patented June 15, 1920.

Application filed October 30, 1918. Serial No. 260,350.

which the solution is subsequently to be emp10 ed.

(/alcium may (:|S() I\ a S(), by digesting it with sufficient water tobreak it up and convertit into a mixture of solid calcium sulfate and asolution of sodium sulfate which may be recovered by any well knownmeans.

We declare that what we claim is I The process for the extraction ofsodium sulfate from a saturated or practically saturated solution ofsodium sulfate at any given temperature containing other salts orsubstances, consisting in digesting such solution at or slightly abovesuch temperature with a quantity of hydrated or anhydrous calciumsulfate to form the sulfate and sodium sulfate be recovered from thedouble salt double salt (aS(),Na SO,, and removing sugh precipitate byany well known means.

tically saturated solution of sodium sulfate at any given temperaturecontaining other salts or substances, consisting in digesting suchsolution at or slightly above such temperature with a quantity of asoluble calcium salt, to form the double salt (aS() Na S() and removinpsurii precipitate by any well known means.

3. The process for removing sodium sulfate from solutions containingother salts or substances which consists in adding calcium sulfate toform the double sal (.aSOQNa SLL and then digesting sai double salt withsufficient water to decom= pose it into a solution of sodium sulfate anda precipitate of calcium sulfate, and recovering such calcium sulfateand sodium sulfate by any well known means.

In witness whereof we have hereunto signed our names this 4th dayofOctober, 1918, in the presence of two subscribing witnesses.

FRANCIS ARTHUR FRRETH. HERBERT EDWI'N CfQKSEDGE. Witnesses JOHNMCLACHLAN, H LDA STIRK.

